The invention relates to non-volatile solid state resistive switching devices.
Resistive switching behavior has been observed and studied in layered amorphous silicon (a-Si) devices since the 1980s. A typical metal/a-Si/metal (M/a-Si/M) layered device consists of two metal layers sandwiching an a-Si layer. The a-Si layer serves as a storage medium.
Resistive switching behavior has been characterized in terms of metal filament formation inside the a-Si matrix at positive applied voltages. M/a-Si/M devices typically have micron sized filaments which may prevent them from being scaled down to the sub-100 nanometer range.
M/a-Si/M devices are formed at high-voltages. For example, a ten volt pulse may be applied to form certain M/a-Si/M devices. Such forming may not be well-controlled and permanent damage may occur after initial filament formation. This damage may severely limit device yield and application potential.
Other non-volatile memory device structures, such as ferroelectric random access memory (RAM), magneto-resistive RAM, organic RAM, phase change RAM and conductive bridging RAM, have been explored as next generation memory devices. These devices, however, include materials that are not compatible with existing CMOS processes thus increasing fabrication costs. These devices may also exhibit slow switching speeds, small on/off resistance ratios and poor thermal stability.